An acrylonitrile-butadiene-styrene (ABS) resin including styrene as a main component can have excellent properties in terms of impact resistance, mechanical strength, thermal deformation, gloss, and moldability. The ABS resin is used in various fields including electric/electronic products such as household appliances and office machinery, housings, general goods, and the like.
Recently, there is a growing interest and demand for resins capable of exhibiting both low gloss and smooth texture. Particularly, in automotive interior materials, exterior materials for electronics, and the like, which are frequently touched by hands, or remain in sight for a long time, demand for such resins is being greatly expanded. In addition, as environmental regulation is strengthened, the scope of application of low gloss resins allowing elimination of a painting process and direct molding continues to expand.
In addition, increasingly material products such as automotive interior materials, construction materials, and materials for interior decoration, are required to exhibit both low gloss and heat resistance. Such general-purpose products required to have both low gloss and heat resistance expand their market size along with quality enhancement thereof.
As a method of preparing such a heat resistant low gloss resin, particularly a heat resistant low gloss ABS resin, a method in which some components of an ABS resin are replaced by a heat resistant copolymer including a styrene monomer, an imide monomer, and the like, having good heat resistance, to enhance heat resistance of the resin while also using matting additives (matting agents), is most widely used.
For example, there is a method in which a heat resistant resin, such as an α-methylstyrene-styrene-acrylonitrile (AMS-SAN) copolymer or an N-phenylmaleimide-styrene-acrylonitrile (PMI-SAN) copolymer, and inorganic fillers, an acrylic resin or a crosslinked styrene resin for providing low gloss properties are subjected to melt extrusion along with other ABS resin raw materials, thereby preparing a heat resistant low gloss ABS resin. Alternatively, a heat resistant ABS resin is prepared using the heat resistant copolymer as set forth above, followed by post-processing to remove gloss.
In addition, there is a method wherein a micro-scaled rough surface is formed by adjusting the size of rubber particles, which are a dispersed phase of a resin, in preparation of a heat resistant ABS resin using a heat resistant copolymer. Such a micro-scaled rough surface can scatter incident light, thereby reducing gloss.
Further, as a method for further enhancing heat resistance of a heat resistant ABS resin, there is a method wherein a heat resistance copolymerized resin is prepared using α-methylstyrene (AMS) or N-phenyl maleimide (PMI), followed by melt extrusion of the heat resistant copolymerized resin together with a graft rubber having improved compatibility with a matrix of the heat resistant copolymerized resin and other additives.
However, such a melt extrusion method requires additives capable of providing low gloss properties, in addition to the heat resistance copolymerized resin, so as to realize both low gloss and enhanced heat resistance. Although using additives to realize low gloss is convenient in many ways, there is a problem in that the degree of uniformity in gloss varies depending upon dispersion of the additives, thereby causing deterioration in quality.
Moreover, since such additives generally have high specific gravity, final products also have high specific gravity. Also, the use of expensive matting agents causes unavoidable increase in production cost. Besides the aforementioned methods, injection molding through an etched mold or painting has been used to prepare a heat resistant low gloss ABS resin. However, use of the etched mold requires additional processes resulting in higher production cost, and painting can cause pollution and thus has a disadvantage in terms of environment.
When a typical crosslinking agent, i.e. a silicon compound having at least two unsaturated reactive groups, is included in a resin composition in order to overcome such problems, it is possible to achieve both low gloss and uniformity in appearance. However, since the silicon compound has the same glass transition temperature as a general aromatic vinyl-vinyl cyanide copolymer, it is necessary for the resin composition to further include a highly heat resistant copolymer so as to provide heat resistance.